Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
Plexium, San Diego, CA, USA.
J Clin Endocrinol Metab. 2022 Nov 23;107(11):3100-3110. doi: 10.1210/clinem/dgac493.
Aberrant biosynthesis and secretion of the insulin precursor proinsulin occurs in both type I and type II diabetes. Inflammatory cytokines are implicated in pancreatic islet stress and dysfunction in both forms of diabetes, but the mechanisms remain unclear.
We sought to determine the effect of the diabetes-associated cytokines on proinsulin folding, trafficking, secretion, and β-cell function.
Human islets were treated with interleukin-1β and interferon-γ for 48 hours, followed by analysis of interleukin-6, nitrite, proinsulin and insulin release, RNA sequencing, and unbiased profiling of the proinsulin interactome by affinity purification-mass spectrometry.
Cytokine treatment induced secretion of interleukin-6, nitrites, and insulin, as well as aberrant release of proinsulin. RNA sequencing showed that cytokines upregulated genes involved in endoplasmic reticulum stress, and, consistent with this, affinity purification-mass spectrometry revealed cytokine induced proinsulin binding to multiple endoplasmic reticulum chaperones and oxidoreductases. Moreover, increased binding to the chaperone immunoglobulin binding protein was required to maintain proper proinsulin folding in the inflammatory environment. Cytokines also regulated novel interactions between proinsulin and type 1 and type 2 diabetes genome-wide association studies candidate proteins not previously known to interact with proinsulin (eg, Ataxin-2). Finally, cytokines induced proinsulin interactions with a cluster of microtubule motor proteins and chemical destabilization of microtubules with Nocodazole exacerbated cytokine induced proinsulin secretion.
Together, the data shed new light on mechanisms by which diabetes-associated cytokines dysregulate β-cell function. For the first time, we show that even short-term exposure to an inflammatory environment reshapes proinsulin interactions with critical chaperones and regulators of the secretory pathway.
在 1 型和 2 型糖尿病中，胰岛素前体胰岛素原的异常生物合成和分泌都会发生。炎症细胞因子与这两种形式的糖尿病中胰岛的应激和功能障碍有关，但机制尚不清楚。
我们试图确定糖尿病相关细胞因子对胰岛素原折叠、运输、分泌和β细胞功能的影响。
用人胰岛细胞培养物用白细胞介素-1β 和干扰素-γ 处理 48 小时，然后分析白细胞介素-6、亚硝酸盐、胰岛素原和胰岛素的释放、RNA 测序以及通过亲和纯化-质谱对胰岛素原互作组进行无偏分析。
细胞因子处理诱导了白细胞介素-6、亚硝酸盐和胰岛素的分泌，以及胰岛素原的异常释放。RNA 测序显示，细胞因子上调了内质网应激相关基因，与之一致，亲和纯化-质谱揭示了细胞因子诱导的胰岛素原与多种内质网伴侣和氧化还原酶的结合。此外，在炎症环境中维持适当的胰岛素原折叠需要增加与伴侣免疫球蛋白结合蛋白的结合。细胞因子还调节了胰岛素原与 1 型和 2 型糖尿病全基因组关联研究候选蛋白之间的新相互作用，这些蛋白以前不被认为与胰岛素原相互作用（例如，Ataxin-2）。最后，细胞因子诱导了胰岛素原与微管马达蛋白簇的相互作用，并用诺考达唑化学破坏微管会加剧细胞因子诱导的胰岛素原分泌。
总之，这些数据为糖尿病相关细胞因子失调β细胞功能的机制提供了新的见解。我们首次表明，即使是短暂暴露于炎症环境也会重塑胰岛素原与关键伴侣和分泌途径调节剂的相互作用。
